Tool set for navigating through an electronic book

ABSTRACT

The present invention provides a method for controlling a screen display of an electronic book. The contents of the book are displayed on a screen of the computer system as pages with which the user interacts by a pointer such as a pen or stylus. The navigational tool set performs various functions including one or more of the following: (1) creating page displays for content of the book, (2) providing a navigation interface for identifying material in the book and moving to desired locations, (3) finding character strings located within the book, and (4) accepting handwritten information on pages of the book. The electronic book includes a “bookmark” button which when selected displays a bookmark icon and inserts a bookmark in the book at the page that is currently displayed. Thereafter the user can close the book or move to another page and automatically return to the marked page by selecting the bookmark icon. The user can also move to other pages by scrolling with scroll keys or other navigational devices such as tables of contents browsers and menu pages which are provided on the computer system.

BACKGROUND OF THE INVENTION

The present invention relates generally to methods and apparatus forinteractively displaying book-like documents on pointer-based computersystems such as pen-based computers. The book-like documents may haveone or more tools for navigating through their contents quickly. Thecontents of such documents may include text, graphics, “live” actiontemplates, etc.

A pen-based computer is a small, often hand-held, computer system wherethe primary method for inputting data includes a “pen” or stylus. Atypical pen-based computer system is housed in a generally rectangularenclosure, and has a dual-function display assembly providing a viewingscreen along one of the planar sides of the enclosure. The dual-functiondisplay assembly serves as both an input device and an output device.When operating as an input device, the display assembly senses theposition of the tip of the stylus on the viewing screen and providesthis positional information to the computer's central processing unit(CPU). Some display assemblies can also sense the pressure of the styluson the screen to provide further information to the CPU. When operatingas an output device, the display assembly presents computer-generatedimages on the screen.

The dual-function display assemblies of pen-based computer systemspermit users to operate the computers as a computerized notepads. Forexample, graphical images can be input into the pen-based computer bymerely moving the stylus on the surface of the screen. As the CPU sensesthe position and movement of the stylus, it generates a correspondingimage on the screen to create the illusion that the stylus is drawingthe image directly upon the screen, i.e. that the stylus is “inking” animage on the screen. With suitable recognition software, text andnumeric information can also be entered into the pen-based computersystem in a similar fashion.

Such computer systems have many uses: they can be used to jot down notesat meetings, organize to-do lists, send and receive information byfaxing, electronic mail, etc. Because computer systems such as these arean integral part of many user's lives, it would also be desirable ifthey could be used to store and display book-like information such asnovels and reference materials (i.e., electronic books). This would beespecially desirable in pen-based computer systems which recognizehandwritten instructions and allow the user to scribble handwrittennotes and interact with “live” screens which might be incorporated intothe books.

Suitable materials for use as “electronic books” might includeinteractive almanacs, encyclopedias, and other reference materials suchas lists of phone numbers for various consumer services or governmentagencies. Unfortunately, books and reference materials such as these canbecome large and unwieldy, especially without careful organization.Thus, it would be useful to have specialized tools for navigatingthroughout the content of an electronic book. “Find” methods are nowavailable for searching all text content within a document to locatespecific character strings, but these methods are often too slow orunfocused to quickly take the user to a desired location. It wouldtherefore be desirable to include in electronic books one or morehigh-level navigation systems that quickly show the user where he or sheis located within the book, what other material is available in thebook, and how to get to other locations in the book.

SUMMARY OF THE INVENTION

The present invention provides a method and “content engine” forcontrolling a screen display of an electronic book. The contents of thebook are displayed on a screen of the computer system as “pages” withwhich the user interacts by a pointer such as a pen or stylus. Thecontent engine performs various functions which may include one or moreof the following: (1) creating page displays for content of a “book,”(2) providing a consistent navigation interface for quickly identifyingmaterial in the book and moving to desired locations, (3) findingcharacter strings located within the “book,” and (4) acceptinghandwritten information on pages of the book. These functions can beaccessed by selecting specified buttons, slide bars, menu items, etc.which may appear on the screen continuously or in response to specificuser events. In a preferred embodiment, the content engine displays oneor more pointer-activated buttons on a “status bar” displayed on thescreen. Content or books that might be utilized according to thisinvention includes interactive novels, reference books, encyclopedias,etc.

In a preferred embodiment, the content engine causes a navigation dialogbox to appear on the screen in response to a prompt with the pointer.The navigation dialog box includes a “bookmark” button which whenselected inserts a bookmark in the book at the page that is currentlydisplayed. A bookmark in the context of this invention acts much like abookmark in a conventional book; it marks a page of the book so that theuser can easily return to that page after closing the book or moving toanother page. In the case of an electronic book, the user can close thebook by, for example, selecting a close button or turning off power tothe machine. The user can also move to other pages by scrolling withscroll keys or other navigational devices which are provided on thecomputer system. Once a bookmark is created (by selecting the bookmarkbutton from the navigation dialog box), that bookmark is represented byan icon displayed on the screen within the navigation dialog box. Insome embodiments, the bookmark will be represented as a miniature imageof the page which has been marked. When the user selects the bookmarkfrom the dialog box, the content engine will automatically move to anddisplay the marked page, regardless of which page is currently “open.”

The navigation dialog box may include buttons for other navigationaltools such as a “return to menu” function and a “return to previouspage” function. The menus referred to here are menu or “kiosk” pagesthat include menus of destinations within the book. If the reader islost, he or she can jump to the nearest prior menu page by selecting thereturn to menu button from the navigation dialog box. The system willthen automatically move to the first menu page preceding the currentlydisplayed page. Selecting the “return to previous page” button causesthe page displayed immediately prior to current page to be redisplayed,regardless of where it is located with respect to the current page.

In another aspect, the present invention provides a table of contents orbrowser displayed on the screen. The browser lists “subjects” within thebook in order in which they appear in the book. The user can scroll fromsubject to subject in the browser by selecting up or down scroll arrowsprovided on the computer system. This causes two changes: (1) the pagecurrently displayed is changed to the first available page within thenewly selected subject, and (2) a “you are here” indicator on thebrowser moves so that it points to the new subject. The user can alsomove to the first available page within a subject by selecting thatsubject on the screen (by, e.g., tapping on that subject with a stylus).

The navigation tools at the disposal of the user of this inventioncollectively provide quick, easy methods for showing the user where heor she is located within the book, what other material is available inthe book, and how to get to other locations in the book. In addition,many of these navigation tools allow “live” interaction with the user.“Live” refers to the interaction capabilities of displayed features suchas buttons, dialog boxes, etc., such that a user can select certain ofthese items to take further action (e.g., getting more information aboutthe item or moving to a location). The wide variety of flexible toolsfor moving about within a document is a particular advantage of thisinvention.

In addition to the above-described navigational tools, the presentinvention provides an efficient method for searching or “finding”character strings within a document. Preferably, this is accomplished byfirst displaying a dialog box having a find field. Handwritteninformation written within the find field is then recognized as acharacter string. Of course, other methods of entering a searchablecharacter string may also be employed such as selecting text thatalready exists in a document. Regardless of how the character string isentered, the system encodes it as a collection of trigrams. A trigram isnumerical value obtained by combining unique numerical values for eachof three consecutive letters in a character string. The number oftrigrams encoded in a character string is equal to the number ofcharacters in the string minus 2. Some units of text content within thebook will have premade trigrams for all the information they contain.During a search for the character string, its trigrams are comparedagainst those of potentially searchable text units. If the text unitdoes not have trigrams corresponding to each of the search string'strigrams, it is concluded that the text unit can not contain the searchstring. Such text units are then ignored. If on the other hand, the textunit does contain each trigram of the text string, the unit may containthe search string and a full text search is conducted. In this manner,the system avoids much needless full-text searching of contents thatcannot contain the search string and thereby provides a more efficientsearch routine.

In yet another aspect, the present invention provides methods ofinputting and displaying handwritten material on pages of the book. Forexample, the user can jot personal notes on the pages of the book. Inpreferred embodiments, such notes can be entered and displayed when a“mark-up” button is selected from the computer system. Further, thenotes can be “erased” (i.e., permanently removed from the display) byvarious methods.

These and other features of the present invention will be presented inmore detail in the following specification of the invention and theseveral figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a pen-based computer system in accordancewith the present invention;

FIG. 2 is a pictorial representation of the screen of a computer displayassembly of the present invention;

FIG. 3 is a representation of a computer screen displaying a page of anelectronic book according to this invention;

FIG. 4 is a process flow diagram of the general steps employed ininstalling, displaying, and interacting with a book or referenceaccording to this invention;

FIG. 5 is a process flow diagram detailing the steps employed ininstalling a book in a computer system according to this invention;

FIG. 6 is a process flow diagram showing the decisions employed todetermine whether a book is a “valid” book;

FIG. 7 is a process flow diagram showing how a book can be set up fordisplay according to the present invention;

FIG. 8 is a process flow diagram detailing how a book page can bedisplayed;

FIGS. 9a-c are illustrations of a page description and content recordsused by a computer system of this invention to create a page display;

FIG. 10 is a process flow diagram showing various user inputs that canbe processed in accordance with the present invention;

FIG. 11 is a process flow diagram detailing the process of scrollingthrough pages of a book according to this invention;

FIG. 12 is a process flow diagram detailing the operation of a browseraccording to this invention;

FIG. 13 is an illustration of a screen display showing a browser inaccordance with this invention;

FIG. 14 is an illustration of a screen display showing a browser havingsubject entries with subcategories;

FIG. 15 is a process flow diagram detailing the operation of anavigation dialog in accordance with this invention;

FIG. 16 is an illustration of a screen display showing a navigationdialog box in accordance with this invention;

FIG. 17 is an illustration of a screen display showing a navigationdialog box with a bookmark displayed;

FIG. 18 is an illustration of a screen display showing a kiosk or menupage in accordance with this invention;

FIG. 19 is a process flow diagram detailing the operation of theinvention in “mark-up” mode;

FIG. 20 is an illustration of a screen display in which a book page hashad handwritten notes provided thereon;

FIG. 21 is a process flow diagram detailing the operation of a pagenumber selection feature of this invention;

FIG. 22 is an illustration of a screen display showing a page numberselection dialog box according to this invention;

FIG. 23 is a process flow diagram detailing the steps in which a routingaction is performed according to the present invention;

FIG. 24 is a process flow diagram showing the steps employed inprocessing a live action in accordance with this invention;

FIG. 25 is a process flow diagram detailing the process of executing a“find” search string request according to this invention;

FIG. 26 is a process flow diagram detailing the steps of encoding asearch string as a “trigram” array.

FIG. 27 is a process flow diagram detailing the steps by which a contentrecord is searched for a character string; and

FIGS. 28a and 28 b are illustrations detailing how search strings areencoded as trigrams and used in searches according to the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is well suited for pointer based computer systemssuch as the pen-based, pen-aware and mouse controlled systems that arecurrently popular. For the purposes of illustration, the invention willbe described in connection with a pen-based system.

As shown in FIG. 1, a pen-based computer system 10 in accordance withthe present invention includes a central processing unit (CPU) 12, readonly memory (ROM) 14, random access memory (RAM) 16, input/output (I/O)circuitry 18, and a display assembly 20. The pen-based computer system10 may also optionally include a mass storage unit 22, a keypad (orkeyboard) 24, a serial port 26, an infrared (I/R) port 28, and a clock30.

The CPU 12 is preferably a commercially available, single chipmicroprocessor. While CPU 12 can be a complex instruction set computer(CISC) chip, it is preferable that CPU 12 be one of the commerciallyavailable, reduced instruction set computer (RISC) chips which are knownto be of generally higher performance than CISC chips. CPU 12 is coupledto ROM 14 by a unidirectional data bus 32. ROM 14 preferably containsthe basic operating system for the pen-based computer system 10. CPU 12is connected to RAM 16 by a bi-directional data bus 34 to permit the useof RAM 16 as scratch pad memory. ROM 14 and RAM 16 are also coupled toCPU 12 by appropriate control and address busses, as is well known tothose skilled in the art. CPU 12 is coupled to the I/O circuitry 18 bybi-directional data bus 36 to permit data transfers with peripheraldevices.

I/O circuitry 18 preferably includes a number of latches, registers anddirect memory access (DMA) controllers. The purpose of I/O circuitry 18is to provide an interface between CPU 12 and such peripheral devices asdisplay assembly 20, mass storage 22, keypad 24, serial port 26, and I/Rport 28.

Display assembly 20 of pen-based computer system 10 is both an input andan output device. Accordingly, it is coupled to I/O circuitry 18 by abi-directional data bus 37. When operating as an output device, thedisplay assembly 20 receives data from I/O circuitry 18 via bus 37 anddisplays that data on a suitable screen. The screen for display assembly20 is preferably a liquid crystal display (LCD) of the type commerciallyavailable from a variety of vendors. The input device of displayassembly 20 is preferably a thin, clear membrane which covers the LCDdisplay and which is sensitive to the position of a stylus 38 on itssurface. With such a structure, the membrane of the display assembly 20can serve as an input “tablet.” These position sensitive membranes arealso commercially available. Alternatively, other types of tablets canbe used, such as inductively coupled tablets. Combination displayassemblies such as display assembly 20 which include both the LCD andthe input membrane are commercially available from such vendors asScriptel Corporation of Columbus, Ohio.

Some type of mass storage 22 is generally considered desirable. Massstorage 22 can be coupled to I/O circuitry 18 by a bi-directional databus 40. However, the mass storage 22 can be eliminated by providing asufficient amount of RAM 16 to store user application programs and data.In that case, the RAM 16 can be provided with a backup battery toprevent the loss of data even when the pen-based computer system 10 isturned off. However, it is generally desirable to have some type of longterm mass storage 22 such as a commercially available miniature harddisk drive, nonvolatile memory such as flash memory, battery backed RAM,a PCMCIA card, or the like.

The keypad 24′ can comprise an array of mechanical buttons or switchescoupled to I/O circuitry 18 by a data bus 42. Alternatively, keypad 24′can comprise an entire, standard QWERTY keyboard. In the presentembodiment, a separate keypad 24′ is not used in favor of a “pseudo”keypad 24′. This “pseudo” keypad 24′ comprises “button” areas which areassociated with a bottom edge of the tablet membrane that extends beyondthe lower edge of the LCD display. These button areas are defined by aprinted or silk-screened icons which can be seen through the transparentmembrane of the input tablet. When the “buttons” are selected byengaging the stylus 38 with the membrane over these printed icons, themembrane senses the pressure and communicates that fact to the CPU 12via data bus 37 and I/O 18. An example of pseudo keypad 24′ is shown inFIG. 2.

Other types of pointing devices can also be used in conjunction with thepresent invention. While the method of the present invention isdescribed in the context of a pen-based system, other pointing devicessuch as a computer mouse, a track ball, or a tablet can be used tomanipulate a pointer on a screen of a general purpose computer.Therefore, as used herein, the terms “pointer”, “pointing device”,“pointing means”, and the like will refer to any mechanism or device forpointing to a particular location on a screen of a computer display.

Serial port 26 is coupled to I/O circuitry by a bi-directional bus 44.The serial port 26 can be used to couple the CPU to external devices andnetworks.

Infrared (I/R) port 28 is coupled to I/O circuitry by a bi-directionalbus 46. The I/R port can be used for outgoing information (e.g. tocontrol a printer or some other external device, or to communicate withother computer systems) or for incoming information from other computersor devices.

Clock 30 preferably comprises a real-time clock to provide real-timeinformation to the system 10. Alternatively, clock 30 can simply provideregular clock pulses to, for example, an interrupt port of the CPU 12which can count the clock pulses to provide the time function. However,this alternative clock embodiment tends to be wasteful of CPU processingpower. Clock 30 is coupled to CPU 12 by a data bus 48.

In operation, information is input into the pen-based computer system 10by “writing” on the screen of display assembly 20 with the stylus 38.Information concerning the location of the stylus 38 on the screen ofthe display assembly 20 is input into the CPU 12 via data bus 37 and I/Ocircuitry 18. Typically, this information comprises the Cartesian (i.e.x & y) coordinates of a pixel of the screen of display assembly 20 overwhich the tip of the stylus is positioned. Commercially availablecombination display assemblies such as the aforementioned assembliesavailable from Scriptel Corporation include appropriate circuitry toprovide the stylus location information as digitally encoded data to theI/O circuitry of the present invention. The CPU 12 then processes thedata under control of an operating system and possibly an applicationprogram stored in ROM 14, RAM 16, or mass storage 22. The CPU 12 nextproduces data which is transferred to the display assembly 20 via I/Ocircuitry 18 and data bus 37 to produce appropriate images on the screenportion of the display assembly 20.

In FIG. 2, the pen-based computer system 10 of FIG. 1 is shown housedwithin a generally rectangular enclosure 50. The CPU 12, ROM 14, RAM 16,I/O circuitry 18, and clock 30 are preferably fully enclosed within theenclosure 50. The display assembly 20 (FIG. 1) is mostly enclosed withinthe enclosure 50, but a viewing screen 52 of the display assembly isexposed to the user. As used herein, the term “screen” will refer to theportion of the display assembly 20 which can display an image that canbe viewed by a user. Also accessible to the user is the pseudo keypad24′ that was described with reference to FIG. 1.

The enclosure 50 is preferably provided with apertures 70 which permitthe free transmission of sound from a speaker (not shown) which ishoused within enclosure 50. The speaker can be driven by the CPU 12, byI/O circuitry 18, or by specialized sound chips, as is well known tothose skilled in the art. The speaker can be used to provide userfeed-back, or to transmit audible information to a user.

Upon power-up, pen based computer system 10 displays on screen 52 aninitial “note” area 54 a including a header 53 and a number ofguidelines 58. The header 53 preferably includes a header bar 56 a, thedate of creation of the note area 54 a, and one or more icons and “soft”dedicated header function buttons 51A, 51B, and 51C. The optionalguidelines 58 aid a user in entering text, graphics, and data into thepen-based computer system 10. A graphic object G in the form of atriangle is shown entered within note area 54 a.

Additional note areas, such as a note area 54 b, can be formed bydrawing a substantially horizontal line across the screen 52 with thestylus 38. The substantially horizontal line is recognized by the system10 and is converted into a second header bar 56 b. Additional text,graphical, and other data can then be entered into this second note area54 b. For example, the text object T comprising “ISAAC” has been enteredinto second note area 54 b.

In this preferred embodiment, the keypad 24′, as explained previously,comprises a printed or silk-screened member 60 provided beneath a loweredge of a thin, clear, stylus-sensitive membrane 62 of the input“tablet.” Alternatively, a keypad could comprise a mechanical keypad (orkeyboard) 24, or a keypad could comprise “soft buttons” i.e. imagesgenerated at convenient locations on the screen 52, in which case a“button” would be activated by touching the stylus to the screen overthe image of the button. The keypad 24′ preferably includes a number ofdedicated function buttons 64, an “overview button” 49, and a pair ofscroll buttons 66 a and 66 b. The function buttons 64 include an addressbutton (“Names”), a calendar button (“dates”), a drawer button(“extras”), an undo button, a find button, and an assist button. Theoperation of the note areas 54 a, 54 b, etc., scroll buttons 66 a and 66b, and other aspects of computer system 10 are discussed in greaterdetail in U.S. patent application Ser. No. 07/868,013, now U.S. Pat. No.5,398,310, filed Apr. 13, 1992, and U.S. patent application Ser. No.08/127,211, now U.S. Pat. No. 5,563,996, filed on Sep. 24, 1993 andentitled “Method for Manipulating Notes on a Computer Display,” both ofwhich name Tchao et al. as inventors, are assigned to the assignee ofthe present invention and are incorporated herein by reference in itsentirety.

The screen illustrated in FIG. 2 is referred to as the “notepad”, and ispreferably an application program running under the operating system ofthe pen based computer system 10. In this preferred embodiment, thenotepad is a special or “base” application which is always availablebeneath higher level applications. The notepad application, like otherapplications, runs within a window, which in this instance comprises theentire viewing screen 52. Therefore, as used herein, a “window” is theentire screen or any portion of an entire screen which is dedicated to aparticular application program or a feature of an application program.When the notepad application is running, the address button (names) canthen be used to launch an address book application program. That is,when the address button is depressed, a suitable address bookapplication program is opened and a suitable address book dialog box isdisplayed on screen 52. Similarly, the calendar button (dates) launchesa calendar application program when depressed.

A status bar 68 is provided at the bottom of the notepad application.The status bar 68 may be provided with a number of active and displayareas. For example, U.S. patent application Ser. No. 07/976,970 filedNov. 16, 1992 on behalf of Foster et. al, entitled “Status Bar forApplication Windows” and assigned to the assignee of the presentinvention describes how to make and use the status bar for certainapplications (e.g., a notepad application), and is incorporated hereinby reference in its entirety.

The “Find” button is used to initiate a search for information. The undobutton will undo the latest user action when depressed and will undo thelast two actions if depressed a second time without the intervention ofany additional user actions. The assist button gives the user access toa help menu which is designed to provide operating instructions to theuser that may be helpful when the user is unsure of how to operate thecomputing system.

A “drawer”, which is opened by pressing the drawer button (“extras”) isused to store other application programs, tools, access buttons toexternal ROM cards, communications applications and other items that canbe utilized by the user. When the drawer is “opened”, a drawer dialogbox 55 is displayed on the screen 52 as shown in FIG. 3. The user canthen launch any application stored therein merely by tapping on theassociated icon that is displayed within the drawer dialog box. Thus,the icons serve as “soft buttons” which may be activated by tapping thescreen at a location corresponding to the displayed position of theicon. Of course, in alternative embodiments, the particular applicationsthat are accessed by keypad buttons can be varied widely. For example,additional keys could be added, existing keys removed, and/or the abovedescribed keys could be used to launch different applications.

A plurality of application programs (sometimes referred to as packages)may be stored in the system's memory. By way of example, the notepad, acalendar application, an address book application, a to-do listapplication and a variety of other application programs may be provided.The subject of the present invention, the content engine, may also bestored in the system's memory. The memory may be divided into two ormore discrete sections (sometimes referred to as stores herein), whichrepresent separately addressable segments of memory. By way of example,internal RAM that acts as a first portion of memory may be consideredone store. A PCMCIA card, which can be a part of mass storage 22, may beconsidered a second store. Within each store, much of the data may bedivided into a plurality of different record files (sometimes calledsoups herein). The record files each include a number of records thatare to be used with one or more of he specific application files. In onesuitable embodiment, each page (screen-full) of text constitutes aseparate record, with each record being given a record number that isunique within that application file. Thus, for example, within thecalendar application file, there may initially be thirty records. Theserecords would be given record numbers zero to twenty-nine, respectively.

Preferred embodiments of the present invention employ various “objects.”As is well known to software developers, an “object” is a logicalsoftware unit comprising data and processes which give it capabilitiesand attributes. For example, an object can be queried as to its type andcan return such data as the number of words that it contains, what itsbounding box (BBOX) is, etc. Objects can contain other objects of thesame or of a different type. Objects can also be used to project imageson a screen according to their object type. Example of object types usedin the following description include paragraph, line, and word objects.There are many well known texts which describe object orientedprogramming. See, for example, Object Oriented Programming for theMacintosh, by Kurt J. Smucker, Hayden Book Company, 1986.

In the present invention, objects are preferably implemented as part ofa frame system that comprises frame objects related by a semanticnetwork. A description of semantic networks can be found in “AFundamental Tradeoff in Knowledge Representation and Reasoning”,Readings in Knowledge Representation, by Brachman and Leveseque, MorganKaufman, San Mateo, 1985.

Another preferred tool for implementing the system of the presentinvention is a view system. Various types of view systems are well knownto those skilled in the art. In .the present system, the notepadapplication on the screen 52 forms a first or “root” layer, with thestatus bar 68, for example, positioned in a second layer “over” the rootlayer. The various buttons of the status bar 68 are positioned in athird layer “over” the second and root layers. The view systemautomatically handles “taps” and other gestures of the stylus 38 on thescreen 52 by returning information concerning the tap or gesture and anyobject to which it may be related. Again, the status bar 68 and the viewsystem is described in greater detail in copending U.S. patentapplication Ser. No. 07/976,970, which has been incorporated herein byreference. It is therefore clear that the object oriented programmingand view system software makes the implementation of the processes ofthe present invention less cumbersome than traditional programmingtechniques. However, the processes of the present invention can also beimplemented in alternative fashions, as will be well appreciated bythose skilled in the art.

A preferred embodiment of this invention will now briefly be describedin the context of the figures illustrating various views created onscreen 52. The procedure described below is driven by a “content engine”running on CPU 12. Initially, the user selects a book he or she wishesto read by tapping on the “extras” or “drawer” button of keypad 24′, anextras window then appears on the screen and lists any books that areinstalled in memory. After selecting a book to be read, the book isopened to a “current page.” That is, a record in the book designated as“current page” is displayed on screen 52. A page of an exemplary book(containing a list of “800” phone numbers) is shown in FIG. 3. Theparticular page displayed includes the phone numbers of domestic aircarriers. The “content” 74 of the displayed page includes the actuallist of domestic air carriers and their phone numbers. In addition, thecontent includes a book title “Newton 800 Numbers” with two graphicrepresentations of a telephone and a heading “Domestic Air Carriers”shown in reversed font style.

Displayed at the bottom of the current page is a status bar 76associated with the content engine application. In preferredembodiments, the status bar will appear anytime a book is open. Asshown, the status bar 76 includes a time button 78 (which when selectedshows the date and time), a bookmark button 80, a “mark-up” button 82, apage number button 84, a routing action button 86, and a close button88. The functions of each of these buttons will be described in moredetail below. In addition to the functions provided on status bar 76,the content engine can employ functions that are activated by the scrollbuttons 66 a and 66 b, the overview button 49, and the various functionbuttons 64 (e.g., the undo button, the find button, and the assistbutton).

When the user selects the overview button 49, a table of contents or“browser” window 272 is displayed near the bottom of screen 52 as shownin FIG. 13. The contents include a list of “subjects” (categories ofinformation) 274 found within the book as defined by the author. Asshown in this example, a book of “800” phone numbers includes suchsubjects as international air carriers, auto rental agencies, andexpress mail/package services. At the right side of the contents window,a “You are Here” indicator 276 is displayed. The purpose of thisindicator is to show the user where he or she is located with respect toother subjects within a current book. That is, the indicator shows thesubject area in which the current page resides. As shown in the exampleof FIG. 13, the indicator is pointing to “Domestic Air Carriers,” a listof which is the displayed on the current page. If the “You are Here”indicator moves to a different subject, the current page will become thefirst page within the new subject. In some embodiments, the “Contents”heading 275 at the top of the browser window takes the form of a menuthat lists various browser formats. For example, in addition to thetable of contents view, the browser could also provide an index viewwith page numbers. If the user taps on an index entry, the current pageautomatically becomes the page on which the index entry appears. Otherformats will be apparent to those of skill in the art.

Users can navigate to different subjects within the browser window byeither (1) selecting a given subject in the browser by, for example,tapping on it, or (2) scrolling through the subjects with scroll buttons66 a and 66 b shown in FIG. 2. Each time a new subject is selected bymoving through the browser, two events take place: (1) the current(displayed) page becomes the first page available under the selectedsubject, and (2) the “You are Here” indicator moves such that it pointsto the selected subject. The browser window can be closed by selectingCLOSE button 286.

Some subjects displayed in the browser may contain subcategories whichare displayed when the subject is selected (e.g., tapped). Subjectscontaining subcategories are generally shown in boldface as illustratedin FIG. 14. There, the subjects “Signs of the Zodiac” 278 and “ChineseAstrology” 280 are shown in boldface and, as expected, containsubcategories. In the example shown, “Chinese Astrology,” has beenselected and the subcategories “Year of the Rat” and “Year of the Ox”282 are displayed underneath the subject heading. If the categoryheading is selected a second time, the subcatagories collapse into thecatagory heading (i.e., they disappear). In addition, the currentlydisplayed page reverts to the first page within the category heading (itmay have a different page in the subcategory). In preferred embodiments,subcategories are displayed only if the subject under which they areincluded is directly selected by, e.g., tapping with a stylus. Thus, ifa user scrolls through the various subjects listed in the contentswindow, the subcategories will not be displayed when the indicatorbutton 276 points to a subject having subcategories. In alternativeembodiments, subcategories will be displayed regardless of how thesubjects are selected.

Another navigational aid available to the user is the bookmark or“navigation” window 330 shown in FIG. 16. This window can be opened ondisplay screen 52 by tapping bookmark button 80 in the status bar of thecontent engine. In the embodiment shown, bookmark window 330 includes amark page button 332, a return to previous page button 334, and a returnto menu button 336. In addition, the bookmark window 330 includes aclose button 338 which, when selected, will close the window. If markpage button 332 is selected, a “bookmark” is inserted at the current(displayed) page. The bookmark is preferably represented as a icon inthe form of a miniature version of the marked page and displayed withinbookmark window 330. An exemplary bookmark icon 340 is shown in FIG. 17.When a bookmark is created for a current page, the user can thereafterclose the bookmark window 330 and go about performing other actions.When the user wishes to return to the marked page, he or she simplyopens the bookmark window from anywhere in the book and then selectsbookmark 340 (by, e.g., tapping). The marked page will then immediatelybecome the current page. In preferred embodiments, bookmarks areautomatically removed after a predefined number of new bookmarks havebeen added (e.g. six). In other words, the system only remembers acertain number of bookmarks. In alternative embodiments, individualbookmarks can be removed by the user.

Selecting the return to page button 334 of bookmark window 330 causesthe content engine to change the current page to the immediatelypreceding current page. In other words, the page that had been displayedimmediately before the current page is redisplayed when button 334 isselected. The number of that particular previous page will be shownwithin the return to page button 334. For example, as shown in FIGS. 16and 17, the immediately previous page was page 2 while the current pageis page 3 (as shown in page number button 84).

Selecting the return to menu button 336 of bookmark window 330 causesthe nearest previous menu page to be displayed. In preferredembodiments, the book will include various menu or “kiosk” pagesthroughout its content. Each of these menu pages lists varioussignificant destinations within the book. In some embodiments, theactual name of the menu page (e.g., “airlines,” “computers,” etc.) mayappear in the “return to menu” button. Thus, the button might display“return to airlines” or “return to computers” depending upon where inthe book the user is currently located. An exemplary menu page isillustrated in FIG. 18. As shown, the menus page includes variousentries identified by both name and icon. The actual format of the menupage is up to the individual author. For example, it may contain buttonsrather than names or it may contain no graphics at all. In theembodiment shown, by selecting one of the listed items (e.g., “AutoRental Agencies”), the system moves to the first page listing the autorental agencies contained in the book.

If the user desires to include handwritten notes in the margins or otherlocations of a page, he or she first selects the “mark-up” button 82 toallow handwritten notes to be accepted on the current page. The user isthen free to write anywhere on the screen without affecting the contentsof the displayed page. The user's markings are simply stored as inkobjects on an “overlay” of the current page. The markings can be hiddenby tapping “mark-up” button 82 and then redisplayed by tapping “mark-up”button 82 a second time. In the example shown in FIG. 20, the user'smarkings designate times and flight numbers associated with variousairlines (reference numbers 368 and 366).

In another feature, the user can turn to a specific page by firsttapping on page number button 84 to display a page number dialog box 400as shown in FIG. 22. Within the page number dialog box is a field 404for inserting the desired page number. Typically, the user simply entersthe page number he or she wishes to turn to by writing that number infield 404. The system then recognizes the number and automaticallychanges the current page to the page having the recognized page number.The new current page is then displayed on screen 52 and page numberwindow 400 disappears. The user can also close the page number dialogbox by selecting the close button 402 in the lower right corner of thepage number window.

The process details associated with running interactive books accordingto this invention will now be discussed. An inventory of the installedbooks is maintained by a module known as a “librarian” which resides, atleast in part, in memory of the computer system. In a preferredembodiment, the book content in the form of data structures known as“packages” is routed throughout the computer system The routing processis controlled by via an entity known as a “package manager”. Packagesand package managers are discussed in more detail in U.S. patentapplication Ser. No. 08/099,841 filed Jul. 30, 1993 on behalf of Culbertand Welland, entitled STRUCTURE AND PROTOCOL FOR ROUTING INFORMATION INA SYSTEM, and assigned to the Assignee of the present application. Thatapplication is incorporated herein by reference in its entirety for allpurposes.

Referring now to FIG. 4, an overview of the process of installing,opening, and using a book is illustrated according to a preferredembodiment of the invention. The process begins at 100 and proceeds to astep 102 where the book package is installed. After a book package hasbeen installed in step 102, the system determines whether a user hasselected the installed book in a decision step 104. This can beaccomplished by tapping on an icon for the book in the extras drawer. Ifthe user has indeed selected an installed book, the system moves to aprocess step 106 where the selected book is set up. The process of“setting up” a book will be described in more detail below in connectionwith FIG. 7. After set up, the process moves to a step 108 where viewsof the current page of the selected book are created. This step willalso be described in more detail below. A process step 108 then displaysthe views created at step 108 and updates the page button 84. That is,button 84 shown in FIG. 3 is updated to display the number of the pagecurrently appearing on display 52. At this point, the book is open andavailable to process user inputs in a step 112. These inputs can take avariety of forms and are preferably initiated by tapping buttons onstatus bar 76 (shown in FIG. 3) or dedicated function buttons 64 (shownin FIG. 2). These inputs will be described in more detail below. Thebuttons, menus, dialog boxes, etc. displayed on screen 52 during theuser input stage provide various opportunities for the user to close thebook. A decision step 114 determines whether this option has beenelected; that is, whether the selected book has been closed. If so, theprocess is completed at 116. If not, process control simply returns tothe point before step 112 where the system awaits further user inputs.

The process of installing a book package (step 102) will now bedescribed in more detail with reference to FIG. 5. The process begins at120 (which corresponds to starting point 100 in FIG. 4) and proceeds toa process step 122 where the librarian is notified by the packagemanager that a book package has arrived. Next, a decision step 124determines whether the book in the package is a “valid book”. Thisprocess will be described in more detail below with reference to FIG. 6.If decision step 124 determines that a book in the package is indeed avalid book, the process moves to a decision step 126 which determineswhether the book is a “new” book. New books are those books which do notyet have an entry listed in the librarian. As noted above, each time anew book is installed, it is listed in the librarian. The listingremains in place even if the book is removed from the computer system.Eventually, after a predefined number of new books have been installed,the book's listing may be removed from the librarian. In a preferredembodiment, the oldest book may be removed from the librarian's listingafter about six new books have been installed. If decision step 126determines that the book is, in fact, a new book, a process step 128adds an entry for the new book to the librarian. Thereafter, a step 130makes the new book available to the user. That is, the librarian sendsscripts necessary to have an icon for the book appears in the extrasdrawer. The process is then completed at 132 which corresponds to thepoint immediately before decision step 104 in FIG. 4.

If decision step 124 determines that the book in the package is not avalid book, the process moves to a step 134 where the package manager isnotified of the invalid book. This information may be conveyed to theuser by way of, for example, a dialog box appearing on screen 52.Thereafter, the process is completed at 132.

If decision step 126 determines that the book in the package is not anew book (in other words, there is already an entry in the librarian forthe book), the process proceeds directly to step 130 where the book ismade available to the user. The process is then completed at 132.

When the librarian adds a new book entry to its listing (step 128), italso installs any “intelligent assistance” templates that are associtedwith the book. For example, an assist template may respond to the assistcommand “reserve room” by opening the book of toll-free phone numbers tothe page listing hotels, motels, and inns. Intelligent assistanceroutines are described in more detail in U.S. patent application Ser.No. 07/889,225, filed on May 27, 1992, naming Luciw as inventor, andentitled “Deducing User Intent . . . ,” which is incorporated herein byreference for all purposes. Assist templates are simply stored in memoryas scripts for the action. When the book is removed, any associatedintelligent assistance scripts are automatically removed. As notedhowever, the librarian book entry remains even after the book has beenremoved.

The steps involved in determining whether a book is a valid book(decision step 124 shown in FIG. 5) are detailed in FIG. 6. The processbegins at 138 which corresponds to step 122 of FIG. 5. Thereafter, twoquestions may be asked. First, a decision step 140 determines whetherthe book has a title slot, and second a decision step 142 determineswhether the book has an ISBN slot. As used herein, a “slot” is a regionof a frame (in this case a content frame) reserved for a particular typeof information. The title slot is, of course, reserved for the book'stitle. If the alleged book does, in fact, have a title slot, the processproceeds to a decision step 142 which determines whether the books hasan ISBN slot. Most published books in circulation throughout the worldhave an ISBN for identification. Usually, it takes the form of a seriesof numbers separated by dashes. Because an electronic book is in manyregards like a conventional paper and ink book, authors of electronicbooks are encouraged to follow many of the protocols established forconventional books. One of these is obtaining an ISBN. If decision step142 determines that the book does have an ISBN slot, the processproceeds to 144 where the book is deemed valid (i.e., in the processshown in FIG. 5, decision step 124 is answered in the affirmative andthe process moves to decision step 126). If either of decision steps 140and 142 are answered in the negative, step 146 indicates that the bookis invalid. This corresponds to a negative answer to decision step 124in FIG. 5. Thus, the package manager is notified of an invalid book.

The process of setting up a book that has been selected by the user(process step 106 of FIG. 4) is detailed in FIG. 7. The process beginsat 150 which corresponds to a point after decision step 104 in theprocess shown in FIG. 4. Thereafter, the variable “CURRENT BOOK” is setto the selected book in a step 152. The CURRENT BOOK is simply the bookwhich has been opened and is available for display, receiving userinputs, etc. After step 152, the process proceeds to a step 154 whichputs a “framework” around the display of the selected book. A“framework” refers to a standard border that the content engine causesto be displayed around every book page. Part of this frameworkpreferably includes status bar 76 shown in FIG. 3. Of course, otheritems may be incorporated within the framework such as headers andsidebars. Preferably, the framework includes “live” items such asbuttons which process user input. An “interaction” module (independentof the librarian module) is responsible for installing the framework andsupporting the live screen functions.

After the framework has been installed by step 154, the process proceedsto a step 156 which determines the CURRENT PAGE of the selected book. Inpreferred embodiments, the librarian module is responsible for makingthis determination. The CURRENT PAGE may be the first page or a menupage of the selected book. However, this is by no means always true. Forexample, the book may also open to the last displayed page of the bookbefore it was closed. The system simply consults the librarian module todetermine which book page is the current page. Thereafter, the processis completed at 158 corresponding to the point before step 108 in FIG.4.

FIG. 8 details the process of creating views of the current page (step108 of FIG. 4). Preferably, the process is controlled by an entity knownas a “page module” (a counterpart of the librarian and interactionmodules described above). The process begins at 160 and proceeds to astep 162 in which receives a description of the current page. Thedescription will include various blocks describing how content is to bedisplayed on the current page. The blocks and the instructions theyprovide will be described in more detail below. Briefly, a blockdescribes a unit of content such as a graphic object or a textparagraph. From step 162, the process proceeds to a step 164 which setsa variable NBLOCKS equal to the number of blocks in the current page.Next, an iterative loop step 166 initializes a block counter “i” to oneand determines whether “i” is less than or equal to NBLOCKS. If step 166determines that “i” is less than NBLOCKS, the process moves to adecision step 168 which determines whether Block(i) is a text block.This decision is made by looking at the content referenced by Block(i)and determining whether it has a slot indicating that it contains text.If decision step 168 determines that Block(i) is a text block, a processstep 170 creates a paragraph view at the coordinates referred to byBlock(i). Thereafter, process control returns to iterative loop step 166where the counter i is incremented by 1. If decision step 168 determinesthat Block(i) is not a text block, the process proceeds to a decisionstep 172 which determines whether Block(i) is a graphics block. If so, aprocess step 174 creates a picture view at the coordinates referred toby Block(i). Process control then returns to iterative loop step 166where the counter i is incremented by one. If both decision steps 168and 172 respond in the negative, a decision step 176 determines whetherBlock(i) is a “template” or “form”. If decision step 176 determines thatBlock(i) is indeed a template or form, it creates a template asspecified by Block(i). The template may be, for example, a dialog box, abutton, or other “live” screen feature that the author wishes to includein the current page. After the template has been created by step 178,process control returns to iterative loop step 166 where the counter iis incremented by one. In preferred embodiments, the block type will beeither text, graphics, or form. In alternative embodiments, however,other block types might be included such as sounds, movies, animations,and tabular data. If the system encounters such a block (i.e., decisionsteps 168, 172 and 176 are all answered in the negative), the processwill proceed to a step 180 which creates a view for the alternativeblock type. Process control then returns to the iterative loop step 166.

The system continues to loop through all blocks on the current pageuntil i equals NBLOCKS. In other words, the last block on the currentpage has been processed. Thereafter, the process is completed at 182corresponding to step 110 of FIG. 4. At that step, the contents of thecurrent page are displayed on screen 52 according to the views createdat steps 170, 174, 178, and 180.

A paragraph view (created in step 170) is simply a description of thetext information that will be displayed on screen 52. A picture view(created at step 174) is likewise a description of the picture that willbe displayed on screen 52.

The block structure described above is preferably created by anapplication which converts documents such as word processing documentsinto structures that can be read as books by a content engine of thisinvention. The application which creates such books can, but need not,reside on the same computer system as the content engine of thisinvention. Methods of creating electronic books and the block structurereferred herein are described in U.S. patent application Ser. No.08/147,055, now U.S. Pat. No. 5,524,201 filed on the same day as thepresent application, naming the same inventive entity, entitled METHODFOR PREPARING ELECTRONIC BOOKS, and is incorporated herein by referencefor all purposes.

FIG. 9a shows how the blocks might be arranged for a current page. Inthe example shown, the current page is page 5 which includes threeblocks identified as B1, B2, and B3 at the left side of array 184. Eachrow of array 184 corresponds to a different block. The blocks includecoordinates 186 which specify the location on screen 52 where the blockwill be displayed. In addition, they include a content identifier 188which refers to a frame (stored elsewhere) containing the content thatwill ultimately be on the page at the coordinates specified by thearray. In the example shown, content C36 is associated with block 1,content C37 is associated with block 2, and content C38 is associatedwith block 3. As noted the content may take various forms includingtext, graphics, and templates for interactive displays. In some cases,one or more scripts specifying actions to be taken in connection withthe page will be included within page description 184. These actions caninclude, for example, displaying a dialog box if a certain contentwithin the page is selected.

FIG. 9b shows a hypothetical text content frame. First, it includes aslot 161 for the actual text that appears in the content. Next, itincludes a “styles” slot 163 which specifies the style associated witheach character. Typically, each style will be given a code which isspecified in the styles slot beside a character number for the firstcharacter to which the style is applied. The character number istypically an offset from the beginning of the text stream. Thus, if thefifth character of the stream begins a text segment to be displayed inbold-face, the style slot may have code for bold-face adjacent thenumber five (referring to the fifth character of the stream). The textcontent also includes a layout slot 167 which may specify such featuresas whether the text is centered, has borders, forms a sidebar, etc.Further, the text content may also include a scripts slot 165 containingscripts for certain actions to be taken in connection with the textcontent. Still further, various attributes may be associated with anycontent such as one or more colors, a phone number, a food type, a city,etc.

FIG. 9c illustrates a graphics content. The first slot 169 indicatesthat the content is an icon and provides instructions for drawing theicon. The instructions may be in, for example, a bit map, quick drawinstructions, postscript instructions, etc. Next, a layout slot 171specifies that the graphics will be displayed in side-by-side mode. Inaddition, a script slot 173 includes scripts for taking action inconnection with the graphic. The action can include, for example,displaying a particular page or dialog when a user taps on the graphic.Finally, “Food” and “City” attributes associated with the content areprovided in the bottom two slots.

As noted above, many live features including buttons, lists, dialogboxes, etc. may be provided on display screen 52 for processing userinputs. The general step of processing user inputs (step 112 of FIG. 4)is now discussed in greater detail with reference to FIG. 10. Theprocess begins at 200 and involves various possible user interactionswhich are represented by decision steps 202, 204, 206, 208, 210, 212,214, 216, and 218. This list of user inputs is intended to beillustrative rather than all inclusive. Thus, various functionsdifferent from or in addition to those described in FIG. 10 may beprovided in other embodiments. In the preferred embodiment shown, adecision step 202 determines whether or not one of the scroll arrows (66a and 66 b shown in FIG. 2) has been selected. If not, the systemdetermines whether or not the overview button (49 of FIG. 2) has beenselected. If the overview button has not been selected, the systemdetermines whether the bookmark button (button 80 shown in FIG. 3) hasbeen selected. At decision step 208, the system determines whether themark-up button (button 82 of FIG. 3) has been selected. At decision step210, the system determines whether the page number button (button 84 ofFIG. 3) has been selected. At decision step 212, the system determineswhether the routing slip button (button 86 of FIG. 3) has been selected.At decision step 214, the system determines whether the close button(button 88 of FIG. 3) has been selected. If the close button has beenselected, a step 220 closes the book as well as the book readerapplication and the process is completed at 224. At decision step 216,the system determines whether any specific content gestures have beenprovided. At decision step 218, the system determines whether any systemevents need to be processed. A system event may be, for example, a findrequest or an intelligent assistance request associated with functionbuttons 64 shown in FIG. 2. If any of decision steps 202, 204, 206, 208,210, 212, 216, and 218 are answered in the affirmative, the selection isprocessed at a step 208, 205, 207, 209, 211, 213, 217, or 219,respectively. The process is thereafter completed at 224. Each of theseprocessed steps will be described in more detail below.

Although many of the processes (particularly those associated withfunction buttons described herein) are diagrammed in a manner that couldimply that the system checks for certain actions by event loops orpolling, no such limitation is implied. This format has been employed toemphasize that the invention is, in part, directed to processes orprotocols. As is well-known in the art, some object- or frame-basedsystems do not employ polling. Rather, they use a script or templateassociated with each function button which is simply activated uponselecting that button. The template then directs the specific actionassociated with that button; such as displaying dialog boxes, menus,etc. For example, the system might detect a “pen down” event, determinewhat entity (maybe a view) should receive that event, and send a message(e.g., view clicked) to that view. Further, the drawings often show asequence of decision steps pertaining to user events, with the stepshaving a specified order. The actual order may be different from thatdisplayed and may depend only the order in which the user takes certainactions. Thus, the process flow charts provided herein should not beread to imply that the system necessarily checks for user events in theorder listed.

FIG. 11 details the scrolling process (step 203 of FIG. 10). The processbegins at 226 and proceeds to a decision step 228 which determineswhether the down arrow 66 b has been selected. If so, the processproceeds to a decision step 230 which determines whether the currentpage is the last page of the selected book. If it is not, a process step232 increments the current page by one. At this point, the views for thepage are created and displayed as described above. Thereafter, theprocess is completed at 240. If decision step 230 determines that thecurrent page is, in fact, the last page, no change occurs and theprocess is completed at 240.

If the down arrow has not been selected, decision step 228 directs theprocess to another decision step 234 which determines whether the uparrow has been selected. If it has, the process proceeds to a decisionstep 236 which determines whether the current page is the first page. Ifnot, a step 238 sets the current page equal to the current page minusone. Thereafter, views for the preceding page (the new current page) arecreated and displayed as described above, and the process is completedat 240.

FIG. 12 details the processes associated with the table of contents or“browser” (step 205 of FIG. 10). The action of the browser preferably iscontrolled by a browser module (a counterpart of the librarian,interaction, and page modules described above). The process begins at244 and proceeds to a process step 250 which opens the overview dialogbox (i.e., the browser) The overview dialog box can be closed by twodifferent actions: selecting the close button 286 (FIG. 13) or theoverview button 49 (FIG. 2). Thus, two decision steps determine whetherthe overview dialog box is to be closed. First, a decision step 252determines whether the overview button has been selected. Then, adecision step 254 determines whether the close button 286 has beenselected. If either of decision steps 252 or 254 are answered in theaffirmative, the overview box is closed by a process step 256, and theprocess is completed at 270. As long as neither the overview button northe close button have been selected, decision step 258 determineswhether a subject 274 displayed in the overview box has been selected.If so, a decision step 260 determines whether the selected subject hassubtopics. As noted above, subjects having subtopics are displayed inboldface within the overview box. Examples of such subjects 278 and 280are shown in FIG. 14. If decision step 260 determines that the selectedsubject does indeed have subtopics, a process step 262 displays thosesubtopics below the selected subject as shown in FIG. 14. The subtopicsare then available as subjects for selection. After the subtopics havebeen displayed by step 262 (or if the answer to decision step 260 isnegative), the process proceeds to a step 264 which sets the currentpage equal to the first page on which the selected subject appears. Forexample, if the selected subject includes two subtopics, the currentpage will become the first page of the first of the two subtopics. Afterthe current page has been set, views of the contents of that page arecreated and displayed as described above in connection with FIG. 8.Next, a process step 266 moves the “You are Here” indicator 276 suchthat it points to the currently-displayed subject, as explained above.Thereafter, process control returns to a point immediately beforedecision step 252.

If the overview box has not been closed (either by selecting theoverview button 49 or the close button 286) and a subject from theoverview box has not been selected (i.e., decision step 258 is answeredin the negative), a decision step 268 determines whether a scroll button66 a or 66 b has been selected by, e.g., tapping. If so, the currentpage is set equal to the first page on which the new subject appears instep 264. The new subject will then be the subject either preceding orfollowing the current subject depending upon whether the up or downscroll button has been selected. Thereafter, the process moves to step266 which, as described above, moves the indicator button to theappropriate location. Thereafter, process controls return to decisionstep 252. If each of decision steps 252, 254, 258, and 268 is answeredin the negative, the system awaits selection of either the overviewbutton, the close button, a subject from the overview box, or a scrollbutton.

FIG. 15 details the process by which selection of the bookmark button 80is processed. The process begins at 300 and proceeds to a step 302 whichdisplays the bookmark (or “navigation”) dialog box. The user can thentake various actions within the dialog box by tapping one of the liveaction buttons or features shown in FIGS. 16 and 17. Specifically, theuser can select close button 338, “return to menu” button 336, “markthis page” button 332, “return to page _” button 334, or bookmark 340.In addition, the user can take an action outside of navigation dialogbox 330. Whether the user takes any of these steps is depicted bydecision steps 304, 306, 310, 314, 318, and 324 in FIG. 15. Each useraction will elicit a system response followed by closing the dialog box.

After the dialog box has been displayed in the depicted process, adecision step 304 determines whether the close button (button 338 ofFIG. 16) has been selected. If so, a step 306 closes the bookmark dialogbox and the process is completed at 328. If the close button has notbeen selected, the process proceeds to a decision step 306 whichdetermines whether the user has taken any action outside of the dialogbox. For example, the user might select a scroll button 66 a or theoverview button 49, in which case the bookmark dialog box will be closedin step 308. If both decision steps 304 and 306 are answered in thenegative, a decision step 310 determines whether the return to nearestmenu (or other named page) button 336 has been selected. If so, aprocess step 312 searches backwards through the book until the firstmenu page is located. That menu page is then displayed as shown in FIG.18. Process control then proceeds to steps 308 and 328 where the dialogbox is closed and the process is completed. If decision step 310determines that the return to nearest menu button 336 has not beenselected, a decision step 314 determines whether a bookmark 340 (e.g.,340 in FIG. 17) has been selected from dialog box 330. If so, a step 316sets the current page equal to the page of the bookmark and then createsviews and displays the contents of the new current page as describedabove. Thereafter, process control returns to steps 308 and 328 asdescribed above.

If decision step 314 determines that a bookmark has not been selectedfrom the dialog box, the process moves to a decision step 318 whichdetermines whether the “mark this page” button 332 (FIG. 16) has beenselected. If so, a decision step 320 determines whether a bookmarkalready exists for the current page. Because only one bookmark should beinserted in a given page, an affirmative answer to decision step 320results in the system ignoring the request to create a new bookmark. Theprocess then proceeds to steps 308 and 328. If there is no bookmark onthe current page, a process step 322 creates a new bookmark for thecurrent page and returns process control to step 308. If the “mark thispage” button has not been selected, decision step 318 directs theprocess to decision step 324 which determines whether the “return toprevious page” button 334 (FIG. 16) has been selected. If so, a processstep 325 sets the current page equal to the previous page (i.e., thepage displayed immediately before the currently displayed page) anddisplays the previous page (i.e., the new current page) as describedabove. Thereafter, process control returns to step 308. If none of theuser events described in decision steps 304, 306, 310, 314, 318, and 324has occurred (i.e., the answer to each of these steps is negative), thesystem awaits the occurrence of one of them by keeping the dialog boxopen. This is represented by the process control looping back to step304 from step 324 when the answer to step 324 is negative.

FIG. 19 details the procedure employed when the mark-up button isselected at step 208 of FIG. 10. This aspect of the invention allows theuser to jot down notes on the screen without disturbing the underlyingcontent of the page. The writer is, in effect, writing on a transparentoverlay on the displayed page. If the user moves to another page andthen returns to the marked-up page, he or she can redisplay the originalmarks. In some preferred embodiments, any buttons, menus or other “live”features on the screen become inactivated when the mark-up mode isselected.

The process begins at 350 and proceeds to a process step 352 whichhighlights the mark-up button 82 (i.e., it becomes darker) and then to adecision step 354 which determines whether there are any marks on thecurrent page. If so, a screen view is created such that thosealready-existing marks are displayed overlying the current page in aprocess step 356. Regardless of whether there are any existing marks onthe current page, the system moves to a process step 358 which convertssubsequent pen events to marks on the current page. As noted above,these might include notes useful to the user such as times and flightnumbers associated with the various airlines as shown in FIG. 20. Themarks may be provided in various forms depending upon the pen employedand whether any special functions such as color have been selected.

The system will continue to process pen events in step 358 until theuser either selects the mark-up button again or takes another actionoutside of mark-up mode. This is depicted in FIG. 19 in the loopcomprising decision steps 358, 360, and 362. After a pen event has beenprocessed in step 358, decision step 360 determines whether the mark-upbutton has been reselected. If not, the system moves to decision step362 which determines whether an outside action (e.g., scrolling,overview button selection, routing slip button selection, etc.) has beentaken. Assuming no such action has been taken, process control returnsto step 358 where any further pen marks are processed. If decision step360 ever determines that the mark-up button has been reselected, themarks on the page are hidden in a process step 364. This results in a“clean” (unmarked) page as shown in FIG. 3, and the process isthereafter completed at 365. Also if the decision step 362 determinesthat an outside action has been taken, the process moves to step 364where the marks are hidden as mentioned.

FIG. 21 details the procedure resulting when the page number button 84is selected at decision step 210 of FIG. 10. As noted, this functionallows the user to go to a specific page identified by page number. Theprocess begins at 380 and moves to step 382 which displays a page numberdialog box 400 (FIG. 22). As with many of the other user-initiatedfunctions described above, the dialog box may be closed and procedureterminated by selecting a close button (402) or selecting an actionoutside of the dialog box. In this case, these contingencies arerepresented in decision steps 383 and 384 and process step 386. Afterthe dialog box has been opened in step 382, the process moves decisionstep 383 which determines whether an action outside the dialog box hasbeen taken. If not, decision step 384 determines whether the page numberbutton has been reselected. If either of steps 383 or 384 is answered inthe negative, the process move to step 386 which closes the page numberdialog box and terminates the procedure at step 396. As explained in thecontext of the mark-up button 82, actions outside of the dialog boxinclude, for example, scrolling, routing, etc.

Assuming that the dialog box remains open long enough for a user towrite in a page number in field 404 of FIG. 22 (i.e., both decisionsteps 383 and 384 are answered in the negative), a process step 390 willrecognize the page number as written. Various methods and systems forrecognizing handwritten input are well-known. Recognizers are discussedin copending U.S. patent application Ser. No. 08/001,123, filed on Jan.15, 1993, entitled METHOD AND APPARATUS FOR COMPUTERIZED RECOGNITION,and naming Pagallo et al. as inventors and Ser. No. 08/068,443, filed onMay 27, 1993, entitled METHOD AND APPARATUS FOR RECOGNIZING HANDWRITTENWORDS, and naming Beernink as inventor, both of which are incorporatedherein by reference for all purposes. After the recognizer hasidentified the page number written in field 404, a process step 392 setsthe current page equal to the recognized page number. Views for thecurrent page are then created and displayed at process step 394. Thepage number dialog box is also closed and the process is completed at396.

FIG. 23 details the routing process of step 213 shown in FIG. 10. Theprocess starts at 410 and proceeds to a process step 412 which displaysa routing action menu. The system remains in this state until the usertaps the screen 52. At that time, a decision step 414 determines whetherthe user has tapped inside of or outside of the routing action menu. Ifthe user has tapped inside the menu, a process step 416 displays arouting slip for the selected routing action. The routing slip willtypically include various fields for the destination and format of thedocument to be routed. Further details of routing slips and otheraspects of the routing process are described in U.S. patent applicationSer. No. 08/130,049, filed on Sep. 30, 1993, naming Foster et al. asinventors, entitled METHOD FOR ROUTING ITEMS WITHIN A COMPUTER SYSTEM,and assigned to the assignee of the present invention. That applicationis incorporated herein by reference for all purposes. After the routingslip is displayed, any user inputs associated with the routing slip areprocessed in a step 418. Thereafter, a process step 420 performs theselected routing action, and the process is completed at 424. As notedabove, decision step 414 determines whether the user has tapped insidethe menu. If he or she has tapped outside of the menu, the menu isautomatically closed by a process step 422. The process is thencompleted at 424.

FIG. 24 details the steps of processing a gesture as noted at step 217in FIG. 10. The process starts at 430 and proceeds to a decision step432 which determines whether there is an action script associated withthe gesture that has been received. If so, a step 434 executes thataction and the process is completed at 436. If there is no action scriptassociated with the gesture (i.e., decision step 432 is answered in thenegative), the process is completed at 436.

As noted above, book authors may include various templates or formsassociated with pages of their books. These templates may be activatedby the user when he or she selects a button or other “live” feature ondisplay screen 52. The gesture will typically be a simple action such astapping on a button, but may include other actions such as writing,scrubbing (i.e., deleting an item by scribbling over top of it), anddouble tapping.

FIG. 25 details the steps employed to process events at step 219 of FIG.10. “System events” refer to various events that are prompted fromoutside of the content engine. These include, for example, intelligentassistance events, find events, etc. As noted above, intelligentassistance routines are described in more detail in U.S. patentapplication Ser. No. 07/889,225, filed on May 27, 1992, naming Luciw asinventor, and entitled “Deducing User Intent . . . .” The presentinvention employs a particularly efficient “find” process which will bedescribed below.

The process begins at 440 and proceeds to a decision step 442 whichdetermines whether the system event is a “find” event. If not, theprocess moves to a process step 464 which processes any other events(e.g., an intelligent assistance event). If, however, the system eventis a “find” event, a process step 444 displays a “find dialog” box whichmay have various buttons as noted in U.S. patent application Ser. No.07/889,660, filed May 27, 1992, naming Capps, et al. as inventor, andentitled “SEARCHING AND DISPLAYING RESULTS IN A PEN-BASED COMPUTER,” andU.S. patent application Ser. No. 08/001,121, filed Jan. 5, 1993, namingCapps et al. as inventors, and entitled “LOCATING AND DISPLAYINGINFORMATION . . . .” Both of these applications are incorporated hereinby reference in their entirety for all purposes. The “find dialog” boxgenerally includes a field for the user to write in the search string.When the user has done so, a process step 446 recognizes the searchstring as text. As noted above, suitable recognizers are well known inthe art and described in various patent applications incorporate hereinby reference. After the system has recognized the search string, thestring is encoded as an array of “trigrams”. The details of thisprocedure will be described below. Briefly, a trigram is a number thatrepresents a sequence of three consecutive letters in a text string. Thetrigrams for the search string can be compared against trigrams createdfor certain text contents in the book. By first determining whether thetrigrams in the search string are matched by trigrams in the content,the system can determine whether it is worth doing a full search of thecontent. In this way, a significant number of the potentially searchabletext contents can be eliminated from consideration. This significantlyimproves the efficiency of the search.

After the trigram of the search string has been encoded at step 448, theprocess moves to a decision step 450 which determines whether the searchis a global search. Global searches span all books and, in preferredembodiments, all other records in the system regardless of whichapplication they are associated with. If the search is not a globalsearch, it is deemed a “local” search which is directed to the currentbook only. If decision step 450 determines that the search is, in fact,a global search, the process proceeds to step 452 which sets thevariable NBOOKS equal to the number of books currently available in thesystem. Next, an iterative loop step 454 initializes a record counter“i” to one and determines whether “i” is less than or equal to NBOOKS.If it is, a process step 456 sets the variable NCONTS equal to thenumber of contents in the current book being searched, book (i). Next,an iterative loop step 458 initializes a contents counter “j” to one,and determines whether “j” is less than or equal to NCONTS. If it is, aprocess step 460 checks the content of record (j) for occurrences of thesearch string and records any such occurrences for use by the findfunction. Further details of this step will be provided below. Briefly,each content is quickly checked to determine whether it is searchable ornot. Obviously, certain contents such as graphics cannot be searched fora text string, and are therefore ignored. Other contents such as textparagraphs may be searchable, and may have trigrams associated withthem. Contents having arrays of trigrams, the trigrams of the searchstring is compared against the trigrams for the text content. If itmatches, the full text of that content is then searched for the searchstring.

After the content of record(j) has been checked in step 460, the processreturns to iterative loop step 458 where the content counter j isincremented by one. This process continues until all contents in thecurrent book (book (i)) have been checked by process step 460 and jequals NCONTS. At that point, iterative loop step 458 directs theprocess to a decision step 462 which checks whether the search is localor global. If it is global, process control returns to iterative loopstep 454 where the book counter i is incremented by one, and the nextbook is thereafter searched as described above. If, on the other hand,the search is a local search, decision step 462 directs process controlto 466 and the procedure is completed. In global searches, the loopcontrolled by iterative loop step 454 continues until all NBOOKS havebeen checked. Thereafter, the process is complete at step 466.

FIG. 26 details the procedure by which a search string (or other textstring) is encoded as a trigram. Briefly, each text character has anassociated numerical value available in a table. For instance, thevarious ASCII characters will each have an associated, unique numericalvalue. A trigram is encoded by combining the numerical values for eachof three successive characters. The resulting value is not unique forthe three successive characters, but it is different from the trigramvalue for the vast majority of other three letter sequences. Because itis much easier to compare numerical values associated with trigrams thanto do a full text search, the search procedure of this invention firstcompares the search string trigrams against those of the content beforedoing the full text search.

The process is started at 470 and proceeds to a step 472 which sets thevariable NCHAR equal to the number of characters in the search string.Next, an iterative loop step 474 initializes a character counter “i” toone and compares the current value of i to the value NCHAR minus 2. If iis less than or equal to NCHAR minus 2, the process moves to a step 476which sets the first trigram (TRI(i)) equal to a numerical combinationof the numerical character values of each of the three successivecharacters as shown (i.e., 8*(4*VChar(i)+VChar(i+1))+VChar(i+2)). Inbinary, this expression can be described as follows: the binary notationof VChar(i) is left shifted by 2 and then summed with the binarynotation of VChar(i+1); the resulting sum is left shifted by 3 and thensummed with the binary notation of VChar(i+2). The resulting combinationof the three values is provided as a binary eight bit trigram which mayhave a value of between 0 and 255 (in base ten).

Of course other methods of combination are possible, but preferably thechosen method should give an eight bit word. Within this constraint, anumber of alternative methods are possible. For example, in someembodiments, the search string is encoded as an NGRAM representing acombination of two, four, five, or some number of character values otherthan three. In general, NGRAMs comprised of a combination of Ncharacters can be used. However, as the number of characters in an NGRAMincreases, the chances that more combinations of characters will givethe same value of the NGRAM increases, thus decreasing the reliabilityof the NGRAM array in predicting whether there will be a hit in a giventext content record.

After the numerical values for the individual characters are combined instep 476, a process step 478 loads the value of the trigram in a trigramarray being formed for the search string under consideration. Theprocess then returns to iterative loop step 474 where character counteri is incremented by one and compared with the value NCHAR minus 2.Process steps 476 and 478 are repeated for each new character in thesearch string until the character two characters from the end of thesearch string is encountered. At that point, each three-charactersequence in the search string has been uniquely encoded in a trigram,and iterative loop step 474 directs the process to 480 where the processis completed.

The process of checking the content of each record (j) for hits (processstep 460 in FIG. 25) is detailed in FIG. 27. Briefly, each content iscategorized as one of three types: (1) unsearchable; (2) searchable andwithout “hint bits”; and (3) searchable and having “hint bits”. As notedabove, many records such as graphics are unsearchable and can beignored. Searchable records such as standard text records are eitherprovided with or without hint bits. Hint bits are arrays of trigramsencoding all three character sequences within the content. Certainarbitrarily small content records will contain no hint bits. In apreferred embodiment, records small than about 128 bytes will notcontain hint bits. Of course, this cut-off value can be increased ordecreased in other embodiments. Generally, the cut-off size can range inlength between about 128 and 512 bytes.

The process begins at 484 and proceeds to a decision step 486 whichdetermines whether content record (j) is searchable. If not, the processis completed at 494. That is, record (j) is ignored and the next recordis considered (step 458 of FIG. 25). If, on the other hand, decisionstep 486 determines that record (j) is searchable, a decision step 488determines whether record(j) contains hint bits. If so, a decision step490 then determines whether each trigram in the search string appears inthe hint bits for content record (j). If not, content record (j)obviously does not contain the search string, and the process iscompleted at 494. If, on the other hand, each trigram in a search stringdoes, in fact, appear in the hint bits for content record (j), a processstep 492 performs a full search of content record (j). If any hits arefound, these are recorded and reported to the “find” application. Theprocess is then completed at 494, and the next records is consideredaccording to the above process. If decision step 488 determines thatsearchable content record (j) does not have hint bits, the processproceeds directly to step 492 where a full search for the search stringis conducted in record (j). As before, the process is then completed at494.

As is apparent from the above discussion, only two types of contentrecords are subject to a full search for the search string: (1)searchable records that do not have hint bits; and (2) searchablerecords that have hint bits containing matches for each trigram in thesearch string array. Because many searchable records are automaticallyignored (not subjected to a full text search), the process of thisinvention is considerably more efficient than the case in which a fulltext search is conducted for each content record.

FIGS. 28a and 28 b schematically illustrate the process of encoding atrigram for a search string and comparing the resulting trigrams againsthint bits for a content record. As shown in FIG. 28a, a three-characterframe 500 is moved across a text string (in this case, the word“garlic”) to generate the trigram. The first three letters, g, a, r,each have an associated numeric value as shown. In this case, the valuefor g is 7, the value for a is 1 and the value for r is 18. Thedistributed sum of these three numeric values gives 250 which is thefirst entry in the trigram array. The next entry in the trigram array isfor the letters a, r, l. As shown, the trigram value for this sequenceof characters is 188. The trigram value for the letters r, l, i is 681,and the trigram value for the letters, i, c is 459. Together, the fourvalues shown at 250, 188, 681, and 459 comprise the trigram array forthe text string “garlic”. These values are then compared withcorresponding bits in a hints bits record.

FIG. 28b shows how the trigrams might be used if “garlic” was a searchstring. The trigram array 510 for garlic is compared against hint bits512 for a hypothetical text content record. The hint bits are checkedfor occurrences of each entry in trigram array 510. As indicated by thestars in the hypothetical hint bits in this example, each entry for thegarlic trigram would be found in the hint bits. Under thesecircumstances, a full text search of the content record associated withhint bits 512 would be conducted.

While this invention has been described in terms of several preferredembodiments, it is contemplated that alterations, modifications andpermutations thereof will become apparent to those skilled in the artupon a reading of the specification and study of the drawings.Furthermore, certain terminology has been used for the purposes ofdescriptive clarity, and not to limit of the present invention. Forexample, the functions provided with the “navigation” or “bookmark”dialog box could be provided within other dialog boxes, on the statusbar, or even off the screen as one of the function buttons. It istherefore intended that the following appended claims include all suchalterations, modifications and permutations as fall within the truespirit and scope of the present invention.

What is claimed is:
 1. A method of controlling the display of anelectronic book on a display screen of a hand-held stylus-based computerhaving a processor connected to the display screen, a memory connectedto the processor, one or more buttons, and a stylus, the methodcomprising: opening a book package which contains the electronic bookand which resides, at least in part, in the memory of the computer;displaying a view of a current page of the electronic book on thedisplay screen, the view including at least one navigation button;displaying a navigation dialog box on the display screen when thenavigation button is selected by interaction of the stylus with thedisplay screen, the navigation dialog box having at least a bookmarkbutton and a return to menu button; placing a bookmark at a preselectedpage when the bookmark button is selected by interaction of the styluswith the display screen; and displaying a menu page in the electronicbook when the return to menu button is selected by interaction of thestylus with the display screen, the menu page listing one or moredestinations within the electronic book which can be reached byselecting a corresponding destination from the menu page.
 2. The methodof claim 1 further comprising a step of displaying on the display screena view of a destination page when a destination is selected from thedestinations included in the menu page.
 3. The method of claim 1 whereinthe electronic book contains a plurality of menu pages which areprovided by an author of the electronic book throughout its content andthe nearest menu page preceding the current page is displayed when thereturn to menu button is selected.
 4. The method of claim 1 wherein thebook package includes a book title and an ISBN.
 5. The method of claim 1wherein the step of displaying a view of the current page includes astep of creating paragraph views of text content records at predefinedcoordinates on the display screen and creating picture views of graphicscontent records at predefined coordinates on the display screen.
 6. Themethod of claim 5 wherein the text and graphics content records areobjects.
 7. The method of claim 5 further comprising a step of creatinga template specifying a live action for the display screen.
 8. Themethod of claim 1 wherein the navigation dialog box includes a buttonwhich, when selected, displays a page appearing immediately before thecurrent page.
 9. The method of claim 1 further comprising a step ofdisplaying handwritten notes on the current page when a mark-up buttonis selected.
 10. A method according to claim 9 further comprising a stepof removing said displayed handwritten notes from the display screen inresponse to a subsequent selection of the mark-up button after the stepfor displaying the handwritten notes.
 11. The method of claim 1 furthercomprising the steps of displaying a page number dialog box byinteraction of the stylus with the display screen, and thereafterdisplaying a page having a page number which was hand-written in saidpage number dialog box by interaction of the stylus with the displayscreen.
 12. The method of claim 1 wherein the display screen issensitive to the position of the stylus.
 13. The method of claim 1wherein a representation of the bookmark is provided in the navigationdialog box when the bookmark button is selected.
 14. The method of claim12 wherein the representation of the bookmark is a miniature image ofthe preselected page on which the bookmark has been inserted.
 15. Amethod of apprising a user of his or her relative current location in anelectronic book and of controlling the screen display of the electronicbook on a hand-held stylus-based computer having a processor, a displayscreen connected to the processor, a memory connected to the processor,a stylus, and one or more buttons including a browser button and ascroll button, the method comprising: displaying a view of a currentpage of the book on the display screen; displaying a browser on thedisplay screen when the browser button is selected by interaction of thestylus with the display screen, the browser listing a plurality ofsubjects contained in the book, the browser also indicating in which ofsaid subjects the current page resides; and updating the current pagedisplayed when a new subject is selected from the browser by interactionof the stylus with the display screen, the current page being the firstpage on which said new subject appears.
 16. The method of claim 15wherein the display screen is sensitive to the position of the stylus.17. The method of claim 15 wherein the new subject is selected from thebrowser by scrolling through the subjects with a scroll button.
 18. Themethod of claim 17 wherein the new subject is selected from the browserby pointing to the new subject with the stylus.
 19. The method of claim15 further comprising a step of displaying handwritten notes on thecurrent page when a mark-up button is selected.
 20. A method accordingto claim 15 wherein the current subject is indicated to the user by a“you are here” pointer image generated on the display screen anddirected toward the current subject.
 21. A stylus-based hand-heldcomputer system allowing a user to access an electronic book, thecomputer system comprising: processing means; memory means coupled tosaid processing means; display means coupled to said processing means,the display means being sensitive to the position of a stylus; contentsof the electronic book residing, at least in part, in the memory means,the contents being organized into a plurality of pages; means forspecifying one of said plurality of pages as a current page, the currentpage being displayed on the display means; means for marking one or moreof the pages in the book by interaction of the stylus with the displayscreen, those pages that have been marked having associated bookmarkbuttons displayed in a navigation dialog box appearing on the displaymeans when a navigation button is selected; navigation means forchanging the current page to a marked page displaying it when a bookmarkbutton associated with the marked page is selected from the navigationdialog box by interaction of the stylus with the display screen; andwherein the bookmark buttons are represented in the navigation dialogbox as miniature copies of the pages with which they are associated. 22.A stylus-based hand-held computer system allowing a user to access anelectronic book, the computer system comprising: processing means;memory means coupled to said processing means; display means coupled tosaid processing means, the display means being sensitive to the positionof a stylus; contents of the electronic book residing, at least in part,in the memory means, the contents being organized into a plurality ofpages; means for specifying one of said plurality of pages as a currentpage, the current page being displayed on the display means; means formarking one or more of the pages in the book by interaction of thestylus with the display screen, those pages that have been marked havingassociated bookmark buttons displayed in a navigation dialog boxappearing on the display means when a navigation button is selected;navigation means for changing the current page to a marked pagedisplaying it when a bookmark button associated with the marked page isselected from the navigation dialog box by interaction of the styluswith the display screen; and wherein the navigation dialog box includesa button which when selected changes the current page to the page thathad most recently been displayed before the current page.
 23. Astylus-based hand-held computer system allowing a user to access anelectronic book, the computer system comprising: processing means;memory means coupled to said processing means; display means coupled tosaid processing means, the display means being sensitive to the positionof a stylus; contents of the electronic book residing, at least in part,in the memory means, the contents being organized into a plurality ofpages; means for specifying one of said plurality of pages as a currentpage, the current page being displayed on the display means; means formarking one or more of the pages in the book by interaction of thestylus with the display screen, those pages that have been marked havingassociated bookmark buttons displayed in a navigation dialog boxappearing on the display means when a navigation button is selected;navigation means for changing the current page to a marked pagedisplaying it when a bookmark button associated with the marked page isselected from the navigation dialog box by interaction of the styluswith the display screen; and wherein the contents of the electronic bookinclude one or more menu pages which provide navigational assistancewithin the electronic book, the menu page immediately preceding thecurrent page becoming the current page when a menu page button in thenavigation dialog box is selected, and wherein each menu page lists oneor more destinations within the electronic book which can be reached byselecting a corresponding destination from the menu page.